Radio Waves and Physics


From: Greg Newberry (
Date: Sat Sep 06 1997 - 10:50:20 EDT

> "I just love all this Physics stuff. :-) Dweebs gather to the right
> please."
> Chuck- I am on your right!! I love the Physics stuff too. Fortunate
> enough to make a living at it. Professional dweeb, but I know how a lot
> of the world works.
James (and Dweebs!),

I've got a physics question that I don't even know enough about to
formulate correctly!

Several years ago I read, well tried to read the Feynman lectures on
physics. One area that caught my interest and has tormented me since is
that of sound and the changes it goes thru as frequency changes.

The Setup:
Sound travel thru air falls off at the inverse square of the distance.
However at about 120K (not sure the exact freq) the behaviour of these
'sound' waves change. They no longer depend on air as a transport, in
fact they become RF, and follow the known decay rates of RF.

As I remember, despite the explanations given in the lectures, this
transformation area (some frequency) seems to be a of a mystery. It
happens, there are formulas that show it happened, but are there any
plain english explanations that really tell what is happing as the
frequency of audio enters this range, and at slightly higher frequencies
is RF rather than audio?

I guess this is QRP related (HI) as radio waves leave our antenna we
need to know how and where they are going!

Thanks to all who respond. I probably won't understand but I'll collect
and keep the answers.

|  Greg Newberry   |
|  WB7DUO QRP-L #760                            | 
|  NorCal #1899  CQC #465  AR-QRP #65           |

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